At present, mainstream 40G/100G optical modules are basically implemented through free-space coupling technologies based on prisms, lenses, optical filters, and the like, and are characterized in a complicated process, a need for active alignment, high packaging costs, and a great difficulty in larger-scale integration.
On the other hand, a photonic integration technology generally means that active devices (lasers, detectors, optical amplifiers, optical modulators, and the like) and passive devices (optical splitters/combiners, optical filters, optical multiplexers/demultiplexers, and the like) are integrated to implement a monolithic multi-functional optical device technology. The photonic integration technology is considered as a powerful optical module technology in the near future and especially in short-range optical interconnect applications such as data centers. However, how to effectively couple light of a single mode laser to a planar optical waveguide (also known as Planar Lightwave Circuit, PLC) or other silicon-based optical integrated chips is still a big issue at present. In addition to the coupling efficiency, how to make the process simple and practicable and use automatic devices to achieve the effect of reducing costs is also an important issue.